Network systems that provide communication services via multiple networks have been in widespread use in recent years. In such a network system, a relay apparatus is provided in a network-network interface (NNI). In addition, configurations that provide redundancy paths have been proposed in order to improve the reliability of networks.
FIG. 1 illustrates an exemplary network system that provides a communication service via multiple networks. In the example in FIG. 1, a network #1 includes an edge node device 101 and a network #2 includes an edge node device 102. A terminal 111 is included in the edge node device 101 and a terminal 112 is included in the edge node device 102. The network #1 is connected to the network #2 via relay apparatuses 121 and 122.
The network system illustrated in FIG. 1 provides path redundancy. The relay apparatus 121 relays the traffic of a working path and the relay apparatus 122 relays the traffic of a protection path. Specifically, in the network #1, a working path WP1 is set between the edge node device 101 and the relay apparatus 121 and a protection path PP1 is set between the edge node device 101 and the relay apparatus 122. In the network #2, a working path WP2 is set between the edge node device 102 and the relay apparatus 121 and a protection path PP2 is set between the edge node device 102 and the relay apparatus 122. When the network system operates normally (that is, when no failure occurs in the network system), the traffic between the terminal 111 and the terminal 112 is transmitted via the working path WP1, the relay apparatus 121, and the working path WP2. When any failure occurs on the working path WP1 or the working path WP2, the traffic between the terminal 111 and the terminal 112 is transmitted via the protection path PP1, the relay apparatus 122, and the protection path PP2.
Related technologies are described in Japanese Laid-open Patent Publication No. 2002-57713, Japanese Laid-open Patent Publication No. 2005-354592, Japanese Laid-open Patent Publication No. 2008-219690, Japanese National Publication of International Patent Application No. 2010-515316, and Japanese National Publication of International Patent Application No. 2013-535922.